The present invention relates to transducers and, more particularly, to a transducer suited for use in ultrasonic gas flow meters and a method of manufacturing such a transducer.
Meters which utilize ultrasonic transducers to measure the flow of a fluid are well known. For example, in one technique the difference between the time of travel of an ultrasonic wave upstream in a flowing gas and the time of travel of an ultrasonic wave downstream in the flowing gas is used to determined the flow rate of the gas. Ultrasonic transducers are utilized in such technique for receiving and transmitting the ultrasonic waves. Successful introduction of such gas flow meters requires that all manufacturing and production costs be carefully considered. Ultrasonic transducers are also utilized to establish the speed of sound within a gas by transmitting sound waves from the transducer, reflecting them off of a surface at a known distance, and receiving them back by the same transducer. Another technique for establishing the speed of sound within a gas involves transmitting sound waves from one transducer and receiving them at another transducer at a known distance. The time between transmission, reflection and reception in the case of a single transducer, or transmission and reception in the case of multiple transducers, can then be used to calculate the speed of sound within the particular gas.
In known meters the transducer is one of the most costly components for a variety of reasons. Known transducers suffer from a relatively low production yield due to, among other factors, a complex structure and fabrication procedure leading to noticeable property variations. One known type of transducer used in such gas meters includes a quarterwave matching plate covered by a foil cap. Production problems such as inconsistent foil cap pleats and widely varying quarterwave plate dimensions and material properties lead to uncorrectable variations. Further, known transducers are somewhat limited in terms of the gas pressures under which they may be utilized and are not hermetically sealed from the gas stream.
Accordingly, it would be desirable to provide a simple transducer configuration and related method of manufacture which results in higher production yields and lower transducer costs. It would also be desirable to provide a transducer capable of operating under higher gas pressures. A method of manufacturing such transducers for operation within a predetermined frequency range would further be desirable.